I've read and can't recall the reasons its recomended to stay with staggered wheel sizes.(or tires)Considering buying wheels from a member .5x4.75 - 18" - 9.5width - 25mm back space.All the same size on all corners? Thanks for the help.

 

....active handling system codes......

 

There was some speculation that with equal diameter tires front and rear (assuming the tires have the same profile as well as rim size) your car's traction control might trigger because the rear wheel would be spinning faster than expected compared to the front tire.

 

Not concerning the diameter issue...but you do realize those wheels will stick out of the fenders about 3/4"?

You can use the same wheel size all around, no problem...just stagger the tire heights front to rear, otherwise you will have Traction Control issues. Keep the rear tires about 1/2" taller and you'll be fine.

 

I can undestand how ppl say this but I have never had a problem.

my fronts wheels are 18x11 and my rear wheels are 18x12. I run 25.5x11.5x18 tires on all four corners. the wheels are identical tires and diameter and I have never had AH though a code. I have had AH come on in a corner when I was doing about 70 but I just truned AH off.

 

I have run 305/30/18 Hoosiers on 18x10.5s on all four corners without problem. I have even run the worn out Hoosiers in the back with roughly 1/2 tread Hoosiers in the front (which means the back tires were slightly smaller), again, on the 18x10.5s in all four corners. No ABS/AH/TC problem in full or competitive mode.

And now, I'm planning to run 315/30/18 Pirelli PZero Corsa on 18x10.5s, again, in all four corners and I'm not expecting any problem. Car is still in hibernation mode.

 

It may just be the first generation A/H that has this problem.

 

Howdy!

That sounds like a good theory - I've heard about this since I've had C5's, but only changed the wheels on my '03 Z06, and have never experienced any AH weirdness. I've run on track with setups much different than stock (in comp mode) - no problems either.

I have that spreadsheet that circulated that lets you plug in tire/wheel sizes and calculates overall height and front-to-rear variance as a percentage difference. Supposedly, that's the key, is to keep the front/rear ratio the same as stock.

I'm currently running a 275/35, 335/30 on 18's all around with no problems - had the backend get a little loose in the rain, and AH kicked it and worked like it should (even though the spreadsheet shows a 1.9% change) - switching to a 275/35-18 with a 345/30-19 rear which actually indicates a 3% change from stock, though several people are running this with apparetly no problems.

I do wish there was a definitive answer about this - it seems to make *sense* that the AH system would need to calculate front-to-rear rotation differences to sense a problem. Hopefully the new setup won't be a problem!

FWIW, I read that the staggered 17/18 was to keep the smallest diameter possible on front to reduce the height/frontal area while still clearing the brakes (so a 17") and in the rear where that wasn't a concern it was stepped up to an 18 purely for cosmetics.

I'd have to say after having my stock 17/18, now 18 all around, and seeing lots of 18/19 and 19/20 combos, that (IMO) the shape of the C5 is better balanced by having the front to rear staggered fitment!

Cheers!

 

Based from a engineering stand point the staggered 17/18 are also to help the weight transfer from front to back. When you stagger the car the weight is more even on a hard take off, heance that is why all drage cars have small front to large rear tires. Geving that the vett has 51 to 49 balance, when you take off on a hard pull the weight become 50 pluss rear to a 45 pluss front weight. When you put 18 all the way around then you have the balance off when you launch the car. so this is just my two cents from a engineering stand point. So heance i have staggered wheels on my car. Good luck and carrie on the debate!

 

Wasn't the original concept of the staggared wheel sizes for looks not engineering??

 

When i talk to a friend of mine in the engineering at gm he said it was for both. the only why they could try to handle the wheel hop and some other thing was to stagger. Weight transfer is huge on these cars when you are taking off. I my self in my years of cars have tryed to keep min spin and max launch too the point that i have twisted drive shaft and broken rear ends. But when it comes to cars there are many ideas on how to make the best and fastest cars. Just my two cents and it is not worth much, just one engineers stand point. But i have made some very fast cars and it was not alway the one with the most hp that wins it is how fast you get to the other end. I love these cars and love the look of a staggered cars. most of your high end cars have staggered wheels guess i can not be all wrong. So if it make you happy to have 18 or 19 all the way around go for it.

 

I thought it was so you couldn't rotate the tires.

 

ain't that the truth. We see that on the HPDEs or track days on road course as well.
THAT is the real reason.

 

(I thought it was so you couldn't rotate the tires. ) Now that is priceless is it not. They can not even change the tire at the dealer also.

 

I would be hard pressed to believe that the AH uses wheel speed sensors to calculate vehicle intended direction and steering wheel position. What makes sense is to use a yaw sensor coupled with the steering wheel position sensor.

Now, the ABS maybe a different thing. I know that it uses wheel sensors, but I don't know if they are coupled with the yaw sensor, which I highly doubt. The out-of-limit of tire ODs may confuse the ABS ECU, but then again in my case, I have never had a problem.

The traction control is simpler, but it maybe the one that compares the difference in rotational velocities of the front and rear wheels. Relatively (to the stock ratio) smaller rear wheels mean faster rotational velocity of the rears, which may cause the TC ECU to think that the rear wheels are spinning due to losing traction. I can imagine that the stock programming (even in full AH/TC mode) will allow some discrepancy in rotational velocity ratio. Whether the system has a learn mode to tolerate minor tire OD changes, I have no idea.

In any rate, my TC never "complained" even with the rears slightly smaller. So, I don't know. What may work in mine may not work on yours.

2003 Z06 here.

 

Yaw rate sensor input works with your abs system to help manage over steer and under steer by applying brake pressure to compensate at the correct wheel..
Standard on every Corvette, the Active Handling System can actually help correct the vehicle’s direction if the car is not accurately responding to steering input. By combining yaw-rate sensors, the ABS and traction control systems, AHS compares the steering wheel position with Corvette’s actual direction and applies any of the four brakes to help compensate for difference.

 

Glad to see Evil-Twin step in, i knew he would know if anyone here would. Evil-Twin you can pay me later for all the praise.

 

just thought I would add....it's only a standard option on '01 and later

 

You guys that are chiming in about not having problems, could you list the year of your car?

Personally I've never heard of anyone having problems, provided the kept the rear size bigger (even if it's a tiny amount) than the front. Personally I run 25.7" fronts and 26.1" rears which is way tighter than stock (25.7 and 26.7 I think) and I've never had a problem.

I HAVE heard of people getting codes from running a smaller, or same size in the rear though.

Maybe we can put the debate to bed forever. AH gen 1 or gen 2 might be the deciding factor.

Don't forget that just because you don't get a code, doesn't mean everything is hunky dory.

On my old Camaro SS (2000 model year), it came with 275/40/17 all around from the factory. I upgraded tires and put 285/40/17 on the rear (with 275s on the front).

Never had codes or any real issues, but the ABS would kick on while braking in a corner. I'm not talking high speed, I'm talking taking an exit ramp and gently braking. You could feel the ABS pulse even though the tires were NO WHERE NEAR slipping. Extremely annoying, let me tell ya. And I don't know how many people told me that going to those sizes would be fine. I went back to the same size front/rear and the problem disappeared forever.

Just a thought.

Dope

 

i run 18 inch magnesium all around....kept same overall diameter as stock front to rear.....one day after autocross i put rear on front...front on rear....as soon as i hit 10 or so my reduced power lite came on and car would barely move.....after fiddeling for a bit i turned off traction control and problem was gone.....kept it off till i got home and changed the tires back.....no more power light.....this is on an early 98 without active handling......